Once a neural circuit network is damaged by brain injury or spinal cord injury and the network is thereby cut off or results in nerve cell death, the physiological and/or motor functions governed by nerves are lost, and it becomes extremely difficult to restore the neural circuit. However, in order to recover and/or restore various lost functions, the reconstruction of networks among surviving nerve cells is essential, and thus, nerve axons extending from the surviving nerve cells and neurites extending from the nerve axons need to be regenerated. As a substance having an action to allow neurites to elongate, a nerve growth factor (NGF) secreted from nerve cells has attracted attention. NGF is a factor important and necessary for the growth and functional maintenance of nervous tissues. NGF is essential for the maturation and differentiation of sensory and sympathetic nerves in peripheral nerves, and has an action to prevent the degeneration of nerve cells upon brain injury. However, since NGF does not have blood-brain barrier (BBB) permeability, it is said that NGF cannot shift into brain from the periphery or via oral administration.
Conventionally, as non-peptidic neurite outgrowth agents, neurite outgrowth inducers, and neurite outgrowth promoters, the following non-peptidic agents have been known: a neurotrophic factor, which contains a 5-acyl-2-amino-1,3-selenazole analogue and which has a promoting action on the outgrowth of neurites from nerve cells (see patent document 1); a neurotrophic factor, which contains ebselen having a promoting action on the phosphorylation of mitogen-activated protein kinase (ERK1/2) of nerve cells and has a promoting action on the outgrowth of neurites from nerve cells (see patent document 2); a neurite outgrowth agent containing, as an active ingredient, at least one compound selected from the group consisting of coffeic acid and a derivative thereof (see patent document 3); a neurite outgrowth agent containing, as an active ingredient, at least one plant extract selected from the group consisting of rosemary and sage that contain carnosic acid (see patent document 4); a cell death suppressing substance containing lysophosphatidylethanolamine having an action to allow neurites to elongate from nerve cells (see patent document 5); a neurite outgrowth composition, which contains, as a main ingredient, a cell organelle alkalinization agent such as monensin or concanamycin A, and which acts to allow neurites to elongate from motor nerve cells, (see patent document 6); a neurite outgrowth agent containing polyalkoxyflavonoid such as nobiletin or tangeretin (see patent document 7); a neurite outgrowth activator containing a glycosaminoglycan derivative (see patent document 8); a neurite outgrowth agent containing a lactacystin derivative (see patent document 9); a neurite outgrowth agent containing a small molecule heterocyclic ketone or thioester compound (see patent document 10); a neurite outgrowth agent containing derivatives of ganglioside and N-acyl-N-lyso-ganglioside, N′-acyl-N′-lyso-ganglioside, and N,N′-di- or poly-acyl-N,N′-dilyso-ganglioside, in which at least one hydroxyl group of saccharide, sialic acid, and a ceramide residue, except for persulfated derivatives in the hydroxyl, sialic acid and ceramide group of GM1, GD1a, GD1b and GT1b gangliosides (see patent document 11); a neurite outgrowth agent comprising a chondroitin sulfate/dermatan sulfate hybrid chain containing a disaccharide of GlcUA(2S)-GalNAc(4S) (B unit) (see patent document 12); a neurite outgrowth inducer containing a sugar chain having a bisecting GlcNAc, a complex carbohydrate having the aforementioned sugar chain in the structure thereof, a derivative of the aforementioned sugar chain, etc. (see patent document 13); and a neurite outgrowth inducer containing, as an active ingredient, a low-molecular-weight synthetic compound (see patent document 14).